Quantum computing has limits

There are many long-term research efforts
aimed at eventually producing a quantum computer, which would use the traits
of atomic particles like electrons, photons and atoms to compute.

Although it is extremely difficult to use such infinitesimally small
parts, the weird quantum trait of entanglement would allow calculations
to be carried out all at once on a series of numbers, making quantum computers
fantastically fast. In theory, they could solve large problems that could
never be solved by classical computers, including breaking all security
codes.

Researchers from the University of Arkansas and Texas A&M University
have shown that quantum computers, while theoretically useful for very large
problems, are likely to always need very large amounts of power.

According to their calculations, the statistical nature of quantum
data, the practical requirements of inputting data into systems capable
of carrying out entanglement, and the difficulty of error correction,
or checking data, make quantum computers less efficient than classical
computers for all but a few types of problems.

The work appeared in the September, 2003 issue of Fluctuation
and Noise Letters.